Gerald Thomas, 52, speaking after the court hearing said sister was also “disgusted” at the way she had been treated by her employer.

Mr Thomas told the Daily Post that she also had to repay some of her wages to the council.

November was her last wage. “She was paid in December and January but told it was a mistake and she needs to repay the two months,” Mr Thomas said.

His sister needs a wheelchair if walking any distance and can’t drive now and had been unable to care for her father before his death.

“She depends on her partner who is self-employed and hadn’t been able to work while looking after her,” he said.

“It’s scandalous the way the council has treated her. It was an injury at work. She went into work that day, a normal working day, and will never be the same again.”

A family friend described the council's actions as 'heartless'.

A council spokesman said: ”Whilst it would not be appropriate for the council to discuss the details of individual cases, the authority’s long-term sickness absence arrangements mean that staff receive full pay for the first six months of their absence, with a further six months period on half pay.”

On Friday Judge David Hale told Jones, now 20 but 18 at the time of the assault: “This lady has suffered the devastating injuries and is now living in considerable difficulties, financial and physical, because of what you did.”

Jones, living in supported accommodation at Caernarfon, admitted inflicting grievous bodily harm in November 2013. The court heard the defendant lived in a “fantasy world” and had the language ability of a three to four-year-old.

Prosecuting counsel Wyn Lloyd Jones said the victim had been a teaching assistant for 34 years but had been hit, fell to the floor, and was kicked “at least once”. She had “incomplete tetraplegia”.

The attack happened at a sports centre where Jones was going to take part in archery with a group from Ysgol Pendalar in Caernarfon.

Members of staff tried to explain to the teenager that he would need to wear a protective sleeve, but he became agitated.

Mr Lloyd Jones said Miss Thomas had a swollen neck and was taken in pain to Ysbyty Gwynedd at Bangor.

Three days later she collapsed and couldn’t feel her legs. She was taken back to the hospital.

Miss Thomas was then airlifted to a major trauma centre at Stoke on Trent before being transferred to another specialist hospital at Gobowen, where she spent 10 weeks.

She has an acute spinal cord injury which has left her unable to walk unaided.

Defence barrister Matthew Curtis said Jones had full-time carers. When he admitted the offence he had said: ”I’m guilty and I am sorry.”

The judge said: ”If there were ever another incident like this, there would have to be a hospital order.”

He told Jones: ”What you did in temper had a terrible effect on poor Colette Thomas. You have got to remember what you are capable of doing because you are a strong young man. This woman will never be the same again.”